X70管线钢焊接接头在拉伸过程中的力学响应及性能关系

以X70螺旋埋弧焊管焊接接头为研究对象，采用XTDIC系统测量拉伸过程中母材、焊缝和热影响区的实时应变响应情况，并通过粘贴应变片的电测法获得各区域应变分布曲线，以此为基础研究焊接接头各区域协同变形规律。结果表明:在拉应力的作用下，应变主要集中在焊缝区域，应变量远远大于其他区域，焊缝区域彼此咬合、交错分布的晶粒可有效增加晶界与内部位错的流动阻力，具有较高的应变硬化速率。随着外加应力的持续增加，流动应力开始向热影响区扩散，形成应力集中而断裂。研究结果可以为管线钢焊接工艺设计及塑性变形条件下安全评价提供理论基础和试验依据。

Relationship between Mechanical Response and Properties of X70 Pipeline Steel Welded Joints during Stretching

Taking X70 pipeline steel welded joint as the research object, the XTDIC system is used to measure the real-time strain response of the base metal the weld and the heat affected zone during the stretching process. The strain distribution curve of each zone is obtained by electrical measurement method of pasting strain gauges, on the basis of which the coordinated deformation law of each zone of the welded joint is studied. The results show that the strain is mainly concentrated in the weld zone under the action of tensile stress, and the strain variable is much larger than other zones. The staggered grain in weld zone can effectively increase the flow resistance of grain boundaries and internal dislocations, which has a higher strain hardening rate. As the applied stress continues to increase, the flow stress begins to diffuse into the heat affected zone, forming stress concentration and breaking. The research results can provide theoretical and experimental basis for pipeline steel welding process design and safety evaluation under plastic deformation conditions.